Core for metallic casting and composition for same



Patented Ange 13,

UNITED ES PA'l 'E 2,405,650 urlorrica;

colts-Fort METALLIC CASTING AND .comosrrrou FOR SAME Carl E.. Hartwig,Teaneck, and Raymond E. Roehrenbeok, Lyndlmrst; N. J.,' assignorstoSwan-Finch Oil Corporation, a corporation of New York New York, 8.1.,

No Drawing. Applicatlon'Junel'i, 1944,1

Serial No. s assz.

- scams. (c1.22-'-1ss) This invention relates to cores for metalliccastings, particularly for metals such -as'magnesium,-aluminum, andother metals having a melting point below about 1600 F.; and tocompositions for same. q r

Core compositions for metal casting consisting of the well-known linseedoil-kerosene-rosin type formaldehyde has been heretofore proposed as acore binder for light metal casting. Particularly when cores'ofconsiderable size are made, it isnecessary to use about 50% of suchresin with approximately 50% of cereal binder in order to produce onbaking a polymerized core which hassubstantially no tendency to absorbmoisture from the air.

Another object is to provide a core composition which shall eliminate inlarge part the stickiness of the compositions using onlyurea-formaldehyde and shall produce a core having a higher greenstrength than such composition.

The invention comprises the novel products, the specific embodiments ofwhich: are described hereinafter by way of example in accordance withwhich we now prefer to practice the invention.

We have found in accordance with our invention that a core comprisingsand, urea-formaldehyde and a suitable proportion of a calciummagnesi'umligno-sulfonate gives the desired results The calciummagnesium ligno-sulfonate is one of the products obtained from wastesulfite liquor and is sold under the trade name Goulac by RobesonProcess Company. A typical proximate analysis of this Goulac asfurnished by Robeson Process Company is a follows:

rota 100.00

We have found that if a .sufllcient quantity of this latter material isemployed with urea-formaldehyde resin unpolymerized; say in then to B.stage, cores made therewith may be removed from the core boxessubstantially without sticking, re-' sulting in smooth surfaced coresand smooth surfaced castings. The use of such composition thus permitsan increase in core production by decreasing the time and labor consumedin cleaning coreboxes. Y

We havefound also that baked cores made with our composition have a muchhigher resistance to moisture than straight urea-formaldehyde cores.This, we believe"; is due to the fact that the calcium magnesiumligno-sulfonate acts to form a co-polymer with the urea-formaldehyde.

We can not state positively that such co-polymer is formed, but we doknow at the end of the baking period, that a polymerized resin'isobtained which is more resistant to water than the usualformaldehyde-urea polymer and attracts substantially no moistureaccordingly. Furthermore, when straight urea-formaldehyde is used forcores, is is well known that cereal binders are required in many of thecores to provide sumcient green strength for handling prior to baking.By the use of our composition, a greater green strength is acquired,thus permitting elimination of cereal binder in many smaller cores whereit was previously used with the urea-formaldehyde resins and decreasingthe amount of such binder where requiredlin larger cores. Thi isadvantageous in the molding of light metals such as magnesium, etc.,because cereal binder does, not

burn out readily in casting with magnesium or Urea-formaldehyde resin,About 70% to about 30% Calcium magnesium ligno-sulfonate- About 30% toabout 70% of about .5%-to about 1.5% with about 98.5% to v 99.5% sand orsimilar core forming granular material. The combined materials areemployed in the usual manner in making up the core by moistening thesand and binder with water and molding to the desired shape. The coresare then baked at about 325 F. to 350- F. for about 2 hours or more.

The following are specific examples of our invention as we now prefer topractice'it. It is to be understood that the examples are illustrativeand that the invention is not to be restricted Emmple 1 Fifteen parts byweight of urea-formaldehyde resin, designated as BRU 165170-of theBakelite Company, being a partly polymerized resin in the A to .8 stage,ocurring as a white powder, are mixed with parts of a calcium magnesiumligno-sulfonate which is a substantially dry sulfite-lignite evaporatesold as Goulac. This dry powder mixture constitutes the core compositionand is combined in the proportion of about 1% thereof to 99% of drysand, which is then moistened with water and molded into the desiredshape. Thereafter, the shape is baked at about 350 F. for about 2 hoursto polymerize the binder.

Example 2 7.5 parts by weight of urea-formaldehyde resin oi the kindmentioned in Example 1 are mixed with 17.5 parts of a calcium magnesiumlignosulfonate as also described in Example 1. The dry powder mixture iscombined in the proportion of about 1.5% thereof to 98.5% of dry sandwhich is then moistened with water and molded into the desired shape.Thereafter, the molded shape is baked at about 350 F. for about twohours, causing polymerization of the binder.

The ingredients in the above examples may have added thereto otherwell-known ingredients for the purposes stated below. For example, theremay be added for green strength any one or the well-known cerealbinders. which we believe are prepared from various ty es of starches,or clays such as bentonite. Small proportions of, say, up to 3 or 4% offiy-ash may be added to improve the working properties of thecomposition. Oxidation inhibitors such as sulfur, boric acid andfluoride salts may be added.

We claim:

1. A core composition consisting predominantly of sand and containingpartially polymerized 4 urea-formaldehyde resin mixed with but notchemically combined with a calcium magnesium ligno-sulfonate insufficient quantity to reduce substantially the stickiness or the coreand on baking to render it highly resistant to moisture.

2. A sand core composition having a predominant content of sand and abinder constituting about .5% to about 1.5% of the solid material of thecore, said binder consisting of about 70% to about 30% of partiallypolymerized urea-formaldehyde mixed with but not chemically combinedwith about 30% to about 70% of calcium magnesium ligno-sulfonate.

3. A sand core composition having a predominant content of sand and abinder constituting about .5% to about 1.5% of the solid material of thecore, said binder consisting of about of partially polymerizedurea-formaldehyde mixed with but not chemically combined with about 40%of calcium magnesium ligno-sulfonate.

4. A binder composition fo forming sand cores in which the sandpredominates, said binder comprising asubstantially dry partiallypolymerized urea-formaldehyde mixed with but not chemically combinedwith a calcium magnesium ligno-sulfonate.

5. A binder composition for forming sand cores in which the sandpredominates, said binder comprising about 60% to about 40% of asubstantially dry partially polymerized urea-formaldehyde mixed with butnot chemically combined with about 40% to about 60% of calcium magnesiumligno-sulfonate.

6. A binder composition for forming sand cores in which the sandpredominates, said binder comprising about 60% of a substantially drypartially polymerized urea-formaldehyde mixed with but not chemicallycombined with about 40% of calcium magnesium ligno-sulfonate.

CARL E. HARTWIG.

RAYMOND E. ROEHRHBECK.

